1. Field of the Invention
The present invention relates to methods of testing of carbon articles, and more particularly it relates to methods of nondestructive quality control of carbon articles.
2. Description of the Prior Art
There is known a method of nondestructive quality control of carbon articles (see, for example, "Geophysical Methods of Investigation of Oil and Gas Wells" edited by L. I. Pomeranets, Moscos, NEDRA Publishers, 1981, pp. 32-43, 160-186, in Russian). This method includes the steps of exciting acoustic vibrations in each carbon article taken from a group of carbon articles, and in a specimen cut out from at least one carbon article, converting acoustic vibrations in each carbon article and in the specimen into an electric signal having a frequency corresponding to the frequency of the acoustic vibrations, measuring the frequency of the electric signal to determine the frequency of the acoustic vibrations in the specimen and in the corresponding carbon article, determining the rate of propagation of the acoustic vibrations in each carbon article, measuring the specific electric resistance of the carbon articles, establishing the relationship of the rate of propagation of the acoustic vibrations in a carbon article to its specific resistance, determining the range of the rate of propagation of the acoustic vibrations from the range of predetermined values of the specific resistance, and selecting the carbon articles within the range of the rate of propagation of the acoustic vibrations, held representative of the quality of the carbon articles.
According to this method, the measuring of the specific electric resistance of the carbon articles is performed with a quantity of the carbon articles which is commensurate with the quantity of the articles in the whole lot of group, and the relationship of the rate of propagation of the acoustic vibrations in a carbon to its specific electric resistance is established for each carbon article in the lot.
It can be seen, however, that in this method the necessity of measuring the specific electric resistance of each carbon article, followed by establishing the relationship of the rate of propagation of the acoustic vibrations in the carbon article to its specific electric resistance cannot but decrease the rate of quality control of carbon articles and step up the input of labour and effort into the quality control procedure.